1. Field of the Invention
The invention relates to a Stirling engine and an engine system that includes the Stirling engine. More particularly, the invention relates to the structure of a Stirling engine that uses exhaust gas of an internal combustion engine as a high-temperature heat source and the structure of an engine system that includes the Stirling engine.
2. Description of Related Art
With regard to the structure of a Stirling engine, arts that are considered to be associated with the invention are disclosed in, for example, Japanese Patent Application Publication No. 62-247160 (JP-62-247160 A), Japanese Patent Application Publication No. 2004-301102 (JP-2004-301102 A), and Japanese Patent Application Publication No. 2010-255548 (JP-2010-255548 A). In Japanese Patent Application Publication No. 62-247160 (JP-62-247160 A), there is disclosed a double shell-type Stirling engine that includes an inner shell that is in a high-temperature, high-pressure state, and an outer shell that surrounds the inner shell and is filled with a heat insulating liquid. In Japanese Patent Application Publication No. 2004-301102 (JP-2004-301102 A), there is disclosed a Stirling engine having a base plate to which a cylinder and a heater are directly or indirectly fixed, the base plate being fixed to an exhaust pipe. In Japanese Patent Application Publication No. 2010-255548 (JP-2010-255548 A), there is disclosed a cooler structure for a Stirling engine that includes an outer cylinder, an inner cylinder that is formed in the outer cylinder, a cooler tube that is formed between the outer cylinder and the inner cylinder, and a heat insulating member that blocks the transfer of heat generated in the inner cylinder toward the cooler tube.
In a Stirling engine, a heater that exchanges heat between a high-temperature heat source and a working fluid is directly or indirectly fixed to a housing portion. As a result, however, when the housing portion becomes a heat transfer path from the heater, the internal pressure of a crankcase (i.e., the region of the housing portion, in which a crank portion of a crankshaft is provided) may rise due to the reception of heat by a gas in the crankcase. Thus, the work of the Stirling engine may decrease due to a decrease in the pressure difference between the internal pressure of the crankcase and the pressure of the working fluid that is applied to a piston from a top portion side thereof.